1. Field of the Invention
This invention relates generally to the forming of sand cores for casting operations. More specifically, this invention relates to a method and apparatus for forming and shaping sand cores.
2. Description of the Prior Art
The use of cores to form the shape of cast products or molds is well known. Forming methods are known to provide cores with complicated geometries. Such cores are usually formed in a core box composed of corresponding halves which are joined together about a common seam or parting line to define a cavity having the finished or semi-finished shape of the core. The core is formed by introducing a core forming medium, typically sand, into the cavity and a suitable bonding agent which is thermally or catalytically reacted subsequent to its introduction so that the bonding agent will cause the core forming medium to retain the shape of the cavity. After the core has cured, the core box halves are separated and the core is removed. Since each core is typically used in a single casting, it is important to minimize the cost of producing cores.
Before a core is ready to be used in a casting, its shape must meet predetermined tolerances. Obtaining tolerances may require adjustment of the as formed core shape. Such adjustment may include major reshaping or merely removal of irregularities.
The two piece core box operation almost invariably leaves a fin of sand extending about the core at the location of the core box parting line or seam. Consequently, for most core box operations the shape adjustment includes at least a definning step. The definning operation is costly since the usual procedure is to take the core from the core box to a remote station and there remove the fin. Taking the cores from the core forming apparatus to a separate station is inefficient and raises the cost of forming finished cores.
Various methods are known for removing fins from sand cores. U.S. Pat. No. 2,929,120 shows the use of a low pressure jet to blast sand fins from formed cores. Another known method for definning is to manually pass a die or defining plate, having an outline of the finished core, over the periphery of the core and shear off the sand fin. It is also known to use dies in the more extensive shaping of rough formed sand cores. U.S. Pat. No. 1,735,890 shows an apparatus for defining an extruded shape of a core wherein a rough formed core is loaded into the apparatus and passed through a die having the desired shape. U.S. Pat. No. 2,937,421 shows an apparatus that combines the steps of forming a rough core and passing the rough core shape through a finishing die to obtain a very simple final shape. However, neither of these apparatus are directed to the complex geometries associated with many of the cores produced by modern core box operations.